Kentucky Sen. Mitch McConnell easily withstood a challenge from his right flank Tuesday to secure renomination for a sixth term, the first step toward his ultimate goal of leading a new Republican majority in the Senate next year.

Shortly after polls closed Tuesday, the Associated Press called the GOP primary race for McConnell over Matt Bevin, a Louisville businessman who proved unable to tap into tea party frustration with Congress' establishment Republicans.

McConnell now faces what will likely be a more significant challenge in the general election from Kentucky Secretary of State Alison Lundergan Grimes, who glided to the Democratic nomination Tuesday.

The race promises to be one of the most expensive of the midterm election, and will test Grimes' call to replace the man Democrats call the "Guardian of Gridlock" against the Obama administration in this conservative, coal-rich state.

The Kentucky primary was one of the most-watched contests Tuesday, the busiest day of voting so far in this midterm year. Other key races include a crowded contest for the Republican Senate nomination in Georgia and a congressional race in Idaho that marks another test of the Republican establishment's efforts to curtail the influence of outside tea-party-inspired groups.

As it became clear he was on track to win the primary, McConnell has turned his attention to Grimes. His general election pitch relies heavily on his potential status as the next Senate majority leader, while casting the 35-year-old as simply another candidate to help keep President Obama's party in control of the Senate.

Grimes used a recent bus tour of the state to hammer McConnell over his recent comment to a small newspaper that it was not his job to bring jobs to the state. She's also drawn on her potential history-making role as the state's first female senator, a bid to rally a key constituency in a state where Democrats actually outnumber Republicans.

Two recent polls showed Grimes and McConnell evenly matched in the November battle. Both campaigns will now tap into growing war chests in an attempt to frame the November choice on their terms.

Republicans need a net gain of six seats in November to reclaim majority status in the Senate for the first time since 2007. McConnell, should he win his own race, would then be in line to replace Nevada Democrat Harry Reid as majority leader.